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IBM 5150 PC Technical Reference (6025005, August, 1981) (PDF)

IBM 5150 PC Technical Reference (6025005, August, 1981) (PDF)

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I TRANSMIT 'IACUIT I<br />

+5V<br />

~ 4S-"l<br />

Tx DATA ----I~.,..-----------.,:~ :11::1<br />

+5V<br />

RECEIVE CIRCUIT<br />

PIN 18 4---t-.,<br />

OPTO ISOLATOR<br />

5.SK.I1<br />

:>0--- Rx DATA<br />

PIN 25 "'__+--J<br />

+5V<br />

Figure 23. CURRENT LOOP INTERFACE<br />

~<br />

The voltage interface is a serial interface. It supports certain data and<br />

control signals as listed below.<br />

Pin 2<br />

Pin 3<br />

Pin 4<br />

Pin 5<br />

Pin 6<br />

Pin 7<br />

Pin 8<br />

Pin 20<br />

Pin 22<br />

Transmit Data<br />

Receive Data<br />

Request to Send<br />

Clear to Send<br />

Data Set Ready<br />

Signal Ground<br />

Carrier Detect<br />

Data Terminal Ready<br />

Ring Indicate<br />

The adapter converts these signals to/from TTL levels to EIA voltage<br />

levels. These signals are sampled or generated by the communication<br />

control chip. These signals can then be sensed by the system software<br />

to determine the state of the interface or peripheral device.<br />

2-127

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